1. Field of the Invention
This invention generally relates to distributed computing systems and more particularly, to a method and apparatus for the suspension and continuation of remote processes.
2. Related Applications
The following identified U.S. patent applications are relied upon and are incorporated by reference in this application.
Provisional U.S. Patent Application No. 60/076,048, entitled "Distributed Computing System," filed on Feb. 26, 1998.
U.S. patent application Ser. No. 09/044,923; entitled "Method and System for Leasing Storage," filed on the same date herewith.
U.S. patent application Ser. No. 09/044,838, entitled "Method, Apparatus, and Product for Leasing of Delegation Certificates in a Distributed System," filed on the same date herewith.
U.S. patent application Ser. No. 09/044,834, entitled "Method, Apparatus and Product for Leasing of Group Membership in a Distributed System," filed on the same date herewith.
U.S. patent application Ser. No. 09/044,916, entitled "Leasing for Failure Detection," filed on the same date herewith.
U.S. patent application Ser. No. 09/144,933, entitled "Method for Transporting Behavior in Event Based System," filed on the same date herewith.
U.S. patent application Ser. No. 09/044,919, entitled "Deferred Reconstruction of Objects and Remote Loading for Event Notification in a Distributed System," filed on the same date herewith.
U.S. patent application Ser. No. 09/044,938, entitled "Methods and Apparatus for Remote Method Invocation," filed on the same date herewith.
U.S. patent application Ser. No. 09/045,652, entitled "Method and System for Deterministic Hashes to Identify Remote Methods," filed on the same date herewith.
U.S. patent application Ser. No. 09/044,790, entitled "Method and Apparatus for Determining Status of Remote Objects in a Distributed System," filed on the same date herewith.
U.S. patent application Ser. No. 09/044,930, entitled "Downloadable Smart Proxies for Performing Processing Associated with a Remote Procedure Call in a Distributed System," filed on the same date herewith.
U.S. patent application Ser. No. 09/044,917, entitled "Suspension and Continuation of Remote Methods," filed on the same date herewith.
U.S. patent application Ser. No. 09/044,835, entitled "Method and System for Multi-Entry and Multi-Template Matching in a Database," filed on the same date herewith.
U.S. patent application Ser. No. 09/044,839, entitled "Method and System for In-Place Modifications in a Database," filed on the same date herewith.
U.S. patent application Ser. No. 09/044,945, entitled "Method and System for Typesafe Attribute Matching in a Database," filed on the same date herewith.
U.S. patent application Ser. No. 09/044,931, entitled "Dynamic Lookup Service in a Distributed System," filed on the same date herewith.
U.S. patent application Ser. No. 09/044,939, entitled "Apparatus and Method for Providing Downloadable Code for Use in Communicating with a Device in a Distributed System," filed on the same date herewith.
U.S. patent application Ser. No. 09/044,826, entitled "Method and System for Facilitating Access to a Lookup Service," filed on the same date herewith.
U.S. patent application Ser. No. 09/044,932, entitled "Apparatus and Method for Dynamically Verifying Information in a Distributed System," filed on the same date herewith.
U.S. patent application Ser. No. 09/030,840, entitled "Method and Apparatus for Dynamic Distributed Computing Over a Network," and filed on Feb. 26, 1998.
U.S. patent application Ser. No. 09/044,936, entitled "An Interactive Design Tool for Persistent Shared Memory Spaces," filed on the same date herewith.
U.S. patent application Ser. No. 09/044,934, entitled "Polymorphic Token-Based Control," filed on the same date herewith.
U.S. patent application Ser. No. 07/044,915, entitled "Stack-Based Access Control," filed on the same date herewith.
U.S. patent application Ser. No. 09/044,944, entitled "Stack-Based Security Requirements," filed on the same date herewith.
U.S. patent application Ser. No. 09/044,837, entitled "Per-Method Designation of Security Requirements," filed on the same date herewith.
3. Description of the Related Art
A typical distributed computing system makes the services and computing power of many servers available to many different clients over a network. Typically, a client machine accesses processing capabilities on a server machine using a remote procedure call (RPC) system. The RPC system processes the request on the remote machine and returns the desired results to the requesting client. The network used to transmit the request and return the results can be a local area network (LAN), a wide area network (WAN), and can also include the Internet. Sophisticated distributed computing applications on the Internet offer electronic commerce (e-commerce), telecommuting, and interactive entertainment services around the world using this client-server arrangement.
As the distributed computing paradigm grows in usage and popularity it is increasingly important that resources on the server systems are available to fulfill requests made by the client systems. Each request from a client generally causes a server process to designate resources, including one or more threads, to process the requests. A thread, sometimes called a lightweight process, is a separate sequence of instructions within a process having a separate flow of control. The thread must carve out resources from the system as needed to fulfill the particular request. If resources such as memory and data are available, multiple threads can be executed in parallel to fulfill multiple tasks.
Thread schedulers can be used by the process spawning the threads to coordinate parallel execution of the threads based on a thread's priority, state of execution (i.e. sleep, alive, dead, running), and dependencies among the various threads. A thread scheduler on a single processor system distributes the processor's computing power among many threads to provide the illusion that the threads are actually running in parallel. There are many different scheduling techniques which can be used including first-come-first-served, shortest-thread-first, priority scheduling, and preemptive scheduling techniques such as round-robin. Hybrid scheduling techniques which combine these techniques can also be used as needed by the particular implementation. On multiprocessor systems, schedulers associate different threads with different processors to execute threads in parallel and take advantage of the added computing power.
Unfortunately, if these resources are not immediately available, the thread can not continue execution and is blocked from further processing. These blocked threads of execution hold on to server resources, such as memory, as well as the data and control structures associated with the threads themselves. Eventually, the server may run out of threads to allocate incoming client requests. Incoming client requests may be refused and the server will be effectively removed from the distributed computing environment. This blocking scenario can also reduce a servers ability to service existing requests due to overhead associated with denying service to the incoming calls.
Present distributed computing systems are not designed to address this problem of allocating threads. These systems do not release threads and associated resources when a remote server process is blocked waiting for a resource or particular event. Consequently, transaction intensive distributed computing environments can suffer from the blocking scenario described above. For example, assume a server process receives multiple requests to download a file from multiple clients over the Internet. The server process receives multiple threads from the server operating system to process the requests in parallel but the file requested is locked by another process and is not available. A conventional system would block further processing on each thread and wait for the file to be unlocked. The threads on the server would remain idle even though other processes could utilize the thread resources to process other tasks. When the number of threads on a server system are depleted, the server process will deny service to additional clients. Eventually, the server system will have difficulty processing general tasks.
On many distributed computing systems, the inability to allocate threads and other resources can negatively impact overall processing throughput. Even the high-speed bandwidth available on a distributed computing network will go unused if threads and other resources are not allocated efficiently on the server system.
Based on the above limitations found in conventional systems, it is desirable to improve the allocation of threads and other resources used in a distributed computing environment.